Chair: Kent Scarbrough, Tracor Inc. (USA)
Gerald L. Fudge, University of Texas at Dallas (USA)
Darel A. Linebarger, University of Texas at Dallas (USA)
This paper presents a new set of derivative constraints for the generalized sidelobe canceller (GSC) that can be used to reduce sensitivity to steering error. These constraints are designed to flatten the spatial null of the GSC blocking matrix so that for a small steering error, the desired signal is still blocked and the GSC does not experience signal cancellation. With this approach, the steered response of the GSC can be forced to locally approximate any realizable fixed-weight beampattern. A related set of constraints can be used with the eigenvector constraint calibrated GSC to control the steered response for use in the presence of array errors.
Vittorio Murino, University of Genoa (ITALY)
In this paper, a synthesis method aimed at designing an array antenna is proposed. Simulated Annealing (SA), which is a probabilistic methodology to solve combinatorial optimization problems, has been utilized to optimize the position and the weighting coefficients of array elements in order to improve the antenna performances. Sensor position and related weighting coefficients are considered as parameters to be tuned in order to constrain the directivity function (i.e., the beam power pattern) of an antenna to satisfy specific requirements. Conventional beamforming is utilized to compute the beam power pattern having desired properties, such as narrow width of the main lobe, side lobe amplitudes under a certain threshold, etc., taking also into account the need of reducing a small number of sensor and of little spatial aperture. Several results are presented showing a notable improvement of antenna performances utilizing the SA approach with respect to those considered in literature.
G. V. Serebryakov, Institute of Applied Mathematics Cybern. (RUSSIA)
D. V. Sidorovich, Ruhr-University (GERMANY)
C. Mecklenbraeuker, Ruhr-University (GERMANY)
We present in this correspondence the analyses of the interference coherence effects on the performance of antenna array processor, which maximizes the output signal-to-noise ratio (SNR) for a coherent wave. The analytical expression for the optimal weight vector, directional pattern and output SNR is derived as a function of the coherence coefficient, interference power and parameters of the adaptive processor. We show how different models of interference coherence affect the array performance. Finally, to illustrate the theory, several numerical results are given.
E. C. Real, Lockheed Sanders Inc. (USA)
D. P. Charette, Lockheed Sanders Inc. (USA)
The affects of memoryless (no feedback) amplifiers with amplitude non-linearities on the output of transmit beamforming arrays is studied. These studies are limited to small signal cases where the output signal is not undergoing significant compression by the amplifier; and where the amplifier non-linearities can be approximated well by a cubic polynomial. The performance of three optimal beamforming techniques are compared and contrasted when both linear and non-linear amplifiers are used in a two dimensional array. The two dimensional array considered is designed to simultaneously transmit two narrow band signals, at different frequencies, through a common aperture. Attention is focused on the non-linearity induced interaction of the stimulus signals, and the effect this has on the array's outputs as a function of beamforming technique.
Kenbu Teramoto, Saga University
Hikaru Kamiirisa, Akishima Laboratories (JAPAN)
This paper describes a newly proposed image reconstruction algorithm
and experimental results of a 3-D acoustical holographic imaging system
which has an array composed of sparsely distributed transducer elements.
The proposed algorithm based on the POCS reconstructs the images of
reflectivity iteratively. In each step, the estimation [